Ready Steady Eddy

[EddyCurrent]

Spot on, I think there's enough info here and in the other current build logs to embark so I'm going to start ordering some stuff. Rather than add to this in dribs & drabs I'll update at strategic points in the build.
Hopefully I won't have to ask many more questions.

[EddyCurrent]

On the other hand, went back to basics for a rethink, used spreadsheet and this set up should be very strong with not too much metal bashing.

Gantry width 1000mm, 80x80x3 steel box section
Gantry sides 120x80x5 steel box section with top open end plated.
All other plate 20mm aluminium
Rails mounted on front to remove need to have extra brackets if they were placed top and bottom.
150mm travel on Z axis.
Front could have thin slotted plate for chip protection or the whole front could have bellows fitted to cover rails as well.

Rail are spaced at 170mm centres and Z carriages are same spacing vertically
Y rails, not shown, mount directly under plate at bottom of gantry sides.
Hole for Y ballscrew to exit at one end (not shown) may require double plating around it for strength.

Any thoughts on this ? especially best way to engineer the various butt joints at end of each box section.

[JAZZCNC]

Yep that's getting better.!. . . couple of things worth a mention.?

The way you have ballscrews fixed into gantry ends using FF/FK blocks will cause you problems with alignment and getting in and out because it's effectively trapped.
With this design you'll be better with BK/BF blocks either sat on box section or fasten thru sides of blocks into ends.

How you going to fasten the 120x80 box to those plates which I presume are Aluminium.? You'll have to make sure those ends are cut or machined perfectly 90deg otherwise they'll be a pain and if you weld plates on ends and bolt into Aluminium the plate will need milling perfectly flat.

Fastening the ends to gantry box section will also need careful end machining and attention, Esp if bolted together. If you weld it together you'll need to pay very careful attention to it twisting. . . . Personally I'd weld it together then Epoxy level the front so both rails are on the same plane. This way doesn't matter if it twists has the epoxy will remove any so all you need to ensure is that it's square which is easy done with careful measurement.

I'd also increase those little up stand brackets, basicly make them triangles that go at least half way up the Box section height.

[EddyCurrent]

The way you have ballscrews fixed into gantry ends using FF/FK blocks will cause you problems with alignment and getting in and out because it's effectively trapped.
With this design you'll be better with BK/BF blocks either sat on box section or fasten thru sides of blocks into ends.

You're right, I was thinking the gantry sides might be bolted together thus allowing access to fit the ball screw.

How you going to fasten the 120x80 box to those plates which I presume are Aluminium.? You'll have to make sure those ends are cut or machined perfectly 90deg otherwise they'll be a pain and if you weld plates on ends and bolt into Aluminium the plate will need milling perfectly flat.

I can see the 90deg aspect will be a problem whatever method of construction is used. I was thinking of bolting a block to the aluminium that was a tight fit into the box section, then bolt the box section to the block. Welding a bottom plate as you say and milling might be a better idea.

Fastening the ends to gantry box section will also need careful end machining and attention, Esp if bolted together. If you weld it together you'll need to pay very careful attention to it twisting. . . . Personally I'd weld it together then Epoxy level the front so both rails are on the same plane. This way doesn't matter if it twists has the epoxy will remove any so all you need to ensure is that it's square which is easy done with careful measurement.

I was thinking welding would be best, I would make a jig to hold it.

I'd also increase those little up stand brackets, basicly make them triangles that go at least half way up the Box section height.

I had them like that at first, will change back.

[EddyCurrent]

Metal ordered, ball screws etc. ordered (Chai), pondering HIWIN or similar guides but Zapp is easiest to order these from and they have exact lengths I need without having to cut them. Also I (re)decided that I didn't really want a challenge building this machine, I just want it to work as planned so I can use it. With this in mind then I reverted back to the L gantry which I earlier said I didn't like but it simplifies the making of it quite a bit. It will be something like Matt's (kingcreaky) machine with a few changes.

[Jonathan]

Metal ordered, ball screws etc. ordered (Chai), pondering HIWIN or similar guides but Zapp is easiest to order these from and they have exact lengths I need without having to cut them.

Since it seems you're happy to get the rest of the linear motion parts from China, I'm surprised at your choice of supplier for the linear guides. There are quite a few sellers on aliexpress which sell them for a lot less. For example:

BST AUTOMATION - Small Orders Online Store, Hot Selling Ball screws,ballscrew,linear guide and more on Aliexpress.com

Just send them a message with the lengths you want, and make sure you get the right preload - i.e. not zero.

[EddyCurrent]

I didn't ask Chai about the rails because on ebay he seemed to be selling only round rail. I looked at Aliexpress and that's why I'm pondering, sometimes I just like it easy rather than cheapest.

[Clive S]

Have you thought how you will bolt the Z rail blocks and the Y rail blocks on as they appear to clash with each other. It might be better to make the Z back plate wider. ..Clive

[EddyCurrent]

Have you thought how you will bolt the Z rail blocks and the Y rail blocks on as they appear to clash with each other. It might be better to make the Z back plate wider. ..Clive

Thanks, they are kind of close but the bolt holes don't line up so I was thinking they would bolt onto tapped holes in the plate with hex head screws from their own respective sides but as I've never fitted them before it's just a plan until I get the hardware in front of me. Widening the plate would be a useful option.

[JAZZCNC]

Thanks, they are kind of close but the bolt holes don't line up so I was thinking they would bolt onto tapped holes in the plate with hex head screws from their own respective sides but as I've never fitted them before it's just a plan until I get the hardware in front of me. Widening the plate would be a useful option.

I missed this which is unusual for me has it happens often so I'm always watching for it but you didn't have it like that before so didn't pay any attention this time.!! . . . . . Clives correct thou you can't do it you'll need to lower/lift or widen. . . Chicken and Egg problem.???

Regards 90Deg problem then yes needs same attention but milling ends of 80mm box section will need big mill with large tooling. Having plates for gantry sides which bolt to base plate and are held 90deg with bracing brackets is much easier to do.

Welding will be good but will still possibly try to twist when released from Jig. Even then you can't be 100% sure faces of both box sections are exactly on same plane and that's why I'd use epoxy in this situation.